1. Field of the Invention
The present invention relates to an on-vehicle navigation system having a route searching function.
2. Description of Background Information
There is a well known on-vehicle navigation system which is constructed such that map data including road data produced by converting each point on roads of a map to numerical values is stored into a memory medium such as a CD-ROM or the like, a group of map data in an area of a predetermined range including the present location of a vehicle is read out from the memory medium and is displayed on a display as a map of a region around the present location of the vehicle while recognizing the present location of the vehicle, and a vehicle""s location indicative of the present location of the vehicle is automatically displayed on the map.
Since the conventional on-vehicle navigation system constitutes what is called a locating system which merely shows the present location of the vehicle to passengers by means of a display, an on-vehicle navigation system having a function for automatically searching for traveling routes to a destination and for performing guidance has been developed recently. When the route is searched for, a calculating method such as a Dijkstra method or the like for obtaining the shortest distance is generally used. According to this method, weights are produced for a road between crossings in consideration of road attributions such as express highway, distance, road width, and the like and a route in which the sum of the weights is the minimum value is derived as a guiding route.
A conventional route searching function will now be specifically explained. It is now assumed that there are a plurality of roads as shown by solid lines in FIG. 1 and intersection points A, B, . . . , and E are set to points as crossings of the roads. One road between the crossings is now called a xe2x80x9croad unitxe2x80x9d. A numerical value written to each road unit denotes a weight of the road unit. For running from a point xe2x80x9cAxe2x80x9d (selected as a start point) to a point xe2x80x9cBxe2x80x9d; the following three routes 1, 2, and 3 are conceivable.
Route 1: Axe2x86x92Cxe2x86x92B
Route 2: Axe2x86x92Dxe2x86x92B
Route 3: Axe2x86x92Cxe2x86x92Exe2x86x92B
The sum of weights for each route is shown as follows:
Route 1: 3+5=8
Route 2: 8+5=13
Route 3: 3+3+5=11
Among the three routes, since the sum of the weights of the route 1 which is shown by bold lines in FIG. 2 is the minimum, the route 1 is to be selected as a guiding route.
In such a conventional route searching operation, however, there is a problem such that even in such a case that the user, e.g., a driver or the like, can reach the destination in a shorter time by taking a route selected according to the user""s run experiences than following the guiding route, the same route is always automatically selected as a guiding route from the same point to the same destination as long as a new road attribute which changes the weight is not generated.
It is, therefore, an object of the invention to provide an on-vehicle navigation system having a route searching function of selecting a guiding route to a destination in addition to the user""s run experiences.
An on-vehicle navigation system having a route searching function of the invention comprises: first memory means in which road information has been stored; means for searching for a plurality of traveling routes which can be taken between a start point and a destination, from the road information in the first memory means; second memory means for storing preset weights respectively corresponding to road units contained in the road information; discriminating means for discriminating a road unit which a vehicle is running when the vehicle is running; means for generating run experience data indicating that the vehicle has run the road unit discriminated by the discriminating means; third memory means for storing the generated run experience data by correlating it to the discriminated road unit; means for reading out the weight of each road unit in the traveling route and the corresponding road experience data from the second and third memory means for each of the plurality of traveling routes; means for correcting the weight read out for each road unit in the traveling route by the corresponding run experience data for each of the plurality of traveling routes; weight summing means for calculating a sum value of corrected weights corresponding to each of the road units in the traveling route for each of the plurality of traveling routes; and means for selecting a traveling route of which sum value is the minimum from the plurality of traveling routes.
According to the invention, the run experience data indicative of the run experience is formed and stored for each road unit which the vehicle has run, a plurality of traveling routes which can be run between the start point and the destination are searched for at the time of the route searching operation, the weights of the road units in the traveling route and the corresponding run experience data are obtained from the memory means for each of plurality of traveling routes, the weights are corrected by the corresponding run experience data for each road unit in the traveling route for each of the plurality of traveling routes, the sum value of the corrected weights corresponding to the road units in the traveling route is calculated for each of the plurality of traveling routes, and the traveling route of which sum value is the minimum is selected from the plurality of traveling routes.